In general, a prior-art nail gun usually comprises a muzzle disposed at the front end of a nailing device in the main body of the nail gun, a magazine interconnectably disposed at the bottom of the muzzle for accommodating and storing nails. Further, a trigger is disposed on the handle of the main body of the nail gun for controlling the high-pressure airflow inside the nail gun and a firing pin of the nail gun for the shooting. By the shooting force of the firing pin, the nail in the muzzle can be shot into a work piece.
However, when users use such prior-art nail gun, the nails are shot continuously without knowing the current quantity of nails in the magazine. Therefore, after the nails in the magazine are exhausted, users may continue to cock the trigger. Some users even cock the trigger for several times intentionally to make sure there is no nail in the magazine before reloading the magazine with nails. As to the structure of the nail gun, shooting by a firing pin or other firing device without nails in the magazine may have adverse effects on the life of the nail gun or even cause damages to the nail gun.